X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fust-app.c;h=9a766e4ab68e628cbdec4d9f0432ec0b83dea547;hp=331a9d67160d4fee424e4ddb892e1f7057f8983b;hb=93ec662e687dc15a3601704a1e0c96c51ad228c9;hpb=82cac6d2860bfcca162794e47e87fe4e67e3d39f

diff --git a/src/bin/lttng-sessiond/ust-app.c b/src/bin/lttng-sessiond/ust-app.c
index 331a9d671..9a766e4ab 100644
--- a/src/bin/lttng-sessiond/ust-app.c
+++ b/src/bin/lttng-sessiond/ust-app.c
@@ -392,12 +392,22 @@ void save_per_pid_lost_discarded_counters(struct ust_app_channel *ua_chan)
 
 	rcu_read_lock();
 	session = session_find_by_id(ua_chan->session->tracing_id);
-	if (!session) {
-		ERR("Missing LTT session to get discarded events");
-		goto end;
-	}
-	if (!session->ust_session) {
-		ERR("Missing UST session to get discarded events");
+	if (!session || !session->ust_session) {
+		/*
+		 * Not finding the session is not an error because there are
+		 * multiple ways the channels can be torn down.
+		 *
+		 * 1) The session daemon can initiate the destruction of the
+		 *    ust app session after receiving a destroy command or
+		 *    during its shutdown/teardown.
+		 * 2) The application, since we are in per-pid tracing, is
+		 *    unregistering and tearing down its ust app session.
+		 *
+		 * Both paths are protected by the session list lock which
+		 * ensures that the accounting of lost packets and discarded
+		 * events is done exactly once. The session is then unpublished
+		 * from the session list, resulting in this condition.
+		 */
 		goto end;
 	}
 
@@ -541,7 +551,7 @@ ssize_t ust_app_push_metadata(struct ust_registry_session *registry,
 	char *metadata_str = NULL;
 	size_t len, offset, new_metadata_len_sent;
 	ssize_t ret_val;
-	uint64_t metadata_key;
+	uint64_t metadata_key, metadata_version;
 
 	assert(registry);
 	assert(socket);
@@ -571,6 +581,7 @@ ssize_t ust_app_push_metadata(struct ust_registry_session *registry,
 	offset = registry->metadata_len_sent;
 	len = registry->metadata_len - registry->metadata_len_sent;
 	new_metadata_len_sent = registry->metadata_len;
+	metadata_version = registry->metadata_version;
 	if (len == 0) {
 		DBG3("No metadata to push for metadata key %" PRIu64,
 				registry->metadata_key);
@@ -607,7 +618,7 @@ push_data:
 	 * different bidirectionnal communication sockets.
 	 */
 	ret = consumer_push_metadata(socket, metadata_key,
-			metadata_str, len, offset);
+			metadata_str, len, offset, metadata_version);
 	pthread_mutex_lock(&registry->lock);
 	if (ret < 0) {
 		/*